1. Field of the Invention
This invention relates generally to a method of producing and purifying a number of radioactive species from intermediate energy proton spallation reactions on molybdenum (Mo) targets and relates in particular to a method of producing and purifying curie quantities of strontium-82/85. It is a result of a contract with the Department of Energy (contract W-7405-ENG-36).
Strontium-82 (Sr-82) has a half-life of 25 days and decays by pure electron capture to the ground state of its 75-second daughter, rubidum-82. Rubidium-82 (Rb-82) in turn decays by 95% positron emission and 5% electron capture to stable krypton-82, exhibiting several prominent gamma rays. Because such short-lived alkali metal activity is available from a long-lived parent, the availability of Sr-82 is of significant interest for biomedical studies. The useful shelf-life is determined by the activity of Sr-82, while the very short half-life of Rb-82 keeps the radiation dose to the patient low. With a suitable positron imaging device, a system of generating Rb-82 has a considerable number of potential medical applications in cases where repeated, rapid, dynamic blood-flow information would be of value, for example, in investigation of coronary occlusion, cardiac output, arteriography, and tumor vascularity. Thus, because of the above-described uses, large quantities of Sr-82 are needed.
2. Prior Art
In U.S. Pat. No. 3,957,945, Grant et al., a method of producing and purifying Sr-82 obtained from an intermediate energy spallation reaction on a molybdenum target was provided in a 6-step radiochemical procedure. The 6-step combination process of Grant et al., however, has not been found to be suitable for producing large quantities of Sr-82 because the time and volumes involved in steps of that method expanded to unmanageable levels when a large scale operation was attempted.
In U.S. Pat. No. 3,122,414, Horner et al., and in U.S. Pat. No. 3,258,315, Schmitt, a liquid extraction step was used to separate Sr values from solutions such as fission product waste solutions. In U.S. Pat. No. 3,694,369, Orlandini, U.S. Pat. No. 3,218,123, Davis et al., U.S. Pat. No. 3,173,757, Wheelwright et al., and in U.S. Pat. No. 3,154,500, Jansen et al., ion exchange resins were used in various combination processes to perform separations of fission products, which included Sr values. However, in fission and spallation reactions, different starting materials are used and different products are obtained. Thus, because Sr-82,85 is not produced in a fission reaction but rather in a spallation reaction, none of these patents (excluding Grant) provides a method suitable for producing Sr-82,85 in any amount, much less in curie quantities.
Additionally, no prior art method is known which is suitable for producing in relatively pure form all four of the products Y-88, Zr-88, long-lived Rb, and Sr-82,85. And none of the combinations of steps (recited below) which are used in this invention to produce these four products have been known in the art.
Furthermore, the step of dissolution of an irradiated Mo target in H.sub.2 O.sub.2 followed by passing the solution over even a single ion exchange resin has not previously been known.